HTML5 makes offline web apps possible

With advances in HTML5, web apps no longer require an Internet connection — thanks to HTML5’s support of client-side storage, web apps now can run offline in today’s browsers.

“An HTML5 offline application is simply a website that has been configured to store data locally in the user’s browser so that some or all of its functionality is available when the device is not connected to the Internet,” mobile consultant and web evangelist Jonathan Stark explained in a recent interview. “There are several technologies in the HTML5 family of specs that make offline web apps possible — Offline Application Cache, Web SQL Database, Web Storage, etc.”

Browser support, of course, is an essential consideration. “Support for the most critical offline technologies (Offline Application Cache, Web Storage, and Web SQL Database) is very good across both desktop and mobile browsers,” Stark said. “Even so, I recommend treating offline support as a progressive enhancement — if offline support is an absolute requirement for your web app, you’ll probably have to document which browser/OS combinations are explicitly supported and provide ‘best effort’ support for everything else.”

You can find out more about HTML5 and offline web apps at the upcoming O’Reilly webcast, “Building Offline Web Apps with HTML5,” presented by Stark, on Thursday at 10 a.m. PT. Attendees of the webcast should have a working knowledge of HTML and JavaScript, Stark noted, adding that “experience with SQL is helpful if you plan to use Web SQL Database.” You can sign up for the free, hour-long webcast on our O’Reilly Community site.